Method of detaching sealing member of light emitting device

ABSTRACT

A method of detaching a sealing member of a light emitting device which has a substrate, alight emitting element mounted on the substrate and a sealing member that seals the light emitting element, wherein a release layer and/or an air layer is/are provided between the substrate and the sealing member; and the sealing member is detached from the substrate at the release layer and/or the air layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 14/211,400, filed on Mar. 14, 2014, which claims priority toJapanese Patent Application No. 2013-053451, filed on Mar. 15, 2013, theentireties of which are all hereby incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present disclosure relates to a method of detaching a sealing memberof a light emitting device.

2. Description of the Related Art

Conventionally, for the purpose of improving manufacturing yield of alight emitting device, a light emitting element that is found to bedefective after being mounted on a substrate is detached and thenreplaced with a non-defective light emitting element (for example, seeJapanese Patent Application Laid-open No. 2004-349274).

SUMMARY

A method of detaching a sealing member of a light emitting deviceaccording to one embodiment is a method of detaching a sealing member ofa light emitting device which has a substrate, a light emitting elementmounted on the substrate and a sealing member that seals the lightemitting element, wherein a release layer is provided between thesubstrate and the sealing member; and the sealing member is detachedfrom the substrate at the release layer.

Another method of detaching a sealing member of a light emitting deviceaccording to an embodiment is a method of detaching a sealing member ofa light emitting device which has a substrate, a light emitting elementmounted on the substrate and a sealing member that seals the lightemitting element, wherein an air layer is provided between the substrateand the sealing member; and the sealing member is detached from thesubstrate at the air layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a schematic sectional view of a light emitting device andFIG. 1(b) is a schematic sectional view illustrating a method ofdetaching a sealing member according to one embodiment;

FIG. 2(a) is a schematic sectional view of another light emitting deviceand FIG. 2(b) is a schematic sectional view illustrating a method ofdetaching a sealing member according to another embodiment;

FIG. 3 is a schematic sectional view of another light emitting deviceaccording to another embodiment; and

FIG. 4 is a schematic sectional view of another light emitting deviceaccording to another embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Next, embodiments will be described with reference to the drawings(FIGS. 1 to 4).

An light emitting device according to an embodiment includes asubstrate, a light emitting element mounted on the substrate, a sealingmember that seals the light emitting element, and a release layerprovided between the substrate and the sealing member. The sealingmember is detached from the substrate at the release layer.

Another light emitting device according to the present inventionincludes a substrate, a light emitting element mounted on the substrate,a sealing member that seals the light emitting element, and an air layerprovided between the substrate and the sealing member. In addition, thesealing member is detached from the substrate at the air layer.

(Substrates 101, 201, 304, and 401)

The substrate is a member on which the light emitting element ismounted.

The substrate refers to a so-called mounting substrate, package base, orthe like. Materials of the substrate are not particularly limited andexamples thereof include resins such as thermosetting resins andthermoplastic resins (rigid materials including phenolic resin and glassepoxy resin, flexible materials including BT resin, PPA, polyimide, PET,PEN, PVDF, and liquid crystal polymer, and the like), insulatingmaterials such as ceramics and glass, metals such as copper, aluminum,nickel, iron, and tungsten and alloys thereof, and metals and alloyswhose surfaces are subjected to various types of plating or providedwith insulating layers.

The shape of the substrate is not particular limited and preferableexamples include a plate shape, a sheet shape, and a shape having adepressed portion that houses the light emitting element.

The surface of the substrate favorably has a high optical reflectance.Specifically, white insulating material such as epoxy resin, siliconeresin and PPA containing alumina, titanium oxide, or silicon oxide,polyimide film coated by a white resist made of silicone resincontaining titanium oxide, and the like can be used.

On a face of the substrate on which the light emitting element is to bemounted, at least two pieces of wiring that are separated from oneanother exist so as to correspond to a pair of electrodes of at leastone light emitting element. In addition, as long as wiring exists on asurface of the face of the substrate on which the light emitting elementis mounted, wiring may additionally exist on a surface of a faceopposite to the face on which the light emitting element is to bemounted or wiring may be embedded in one layer or many layers inside thesubstrate. A shape of such a wiring pattern is not particularly limitedand various shapes can be adopted.

Materials of the wiring are not particularly limited as long as thematerial is conductive and examples thereof include metals such as gold,silver, copper, nickel, and aluminum or alloys thereof. The wiring maybe formed by plating using these materials or formed using a conductivepaste, a conductive ink, or the like. In addition, the wiring may beformed by laminating these materials. Furthermore, a material with ahigh optical reflectance is favorably used for an outermost surface onwhich the light emitting element is to be mounted. Silver isparticularly preferable.

When the substrate is conductive, the substrate may be used as thewiring.

(Light Emitting Elements 102, 202, 302, and 402)

A semiconductor light emitting element (for example, an LED) can be usedas the light emitting element. A semiconductor light emitting element isconstituted by a laminated structure in which a semiconductor layer of anitride semiconductor such as InN, AlN, GaN, InGaN, AlGaN, and InGaAlN,a III-V group compound semiconductor, or a II-VI group compoundsemiconductor is laminated on a substrate. Examples of the substrate ofthe light emitting element include an insulating substrate made ofsapphire or the like and a conductive substrate made of SiC, GaN, GaAs,or the like.

With a semiconductor light emitting element using an insulatingsubstrate, an n-side electrode and a p-side electrode may be formed onan upper face of the laminated structure. With a semiconductor lightemitting element using a conductive substrate, one of the electrodes(for example, the n-side electrode) may be formed on an upper face ofthe laminated structure and the other electrode (for example, the p-sideelectrode) is formed on a lower face of the laminated structure.

When the light emitting element is flip-chip mounted, a translucentsubstrate made of sapphire or SiC is favorably used. In addition, asshown in FIGS. 2(a), 2(b) and 3, underfills 208 and 308 such as resinmay be provided between the substrate and the light emitting element.

(Joint Members 103, 203, 303, and 403)

The light emitting element according to an embodiment is mounted on thesubstrate or to wiring on the substrate using a joint member.

Known materials can be used as the joint member, and examples ofmaterials that can be used as the joint member include resins such asepoxy resin and silicone resin, resins containing a conductive materialsuch as silver paste and gold paste, solders such as Sn—Ag—Cu basedsolder, Sn—Cu based solder, Sn—Bi based solder, Sn—Zn based solder, andAu—Sn based solder, and bumps of metals such as Au.

In particular, solders are favorably used. By locally heating andmelting solder by laser irradiation or by using a halogen lamp, a hotplate (heater), a hot air blower, a soldering iron, or the like, a lightemitting element determined to be defective can be readily detached. Inaddition, solder is favorable because solder melted by heating can bereadily removed from the substrate, and a light emitting element can bemounted to a same portion after detachment.

After mounting the light emitting element with the joint memberdescribed above, an electrical connection can be made using a conductivewire between an electrode provided on an upper face of the lightemitting element and the wiring. Favorable examples of such wiresinclude thin wires made of a metal such as Au, Ag, Al, and Cu, alloysthereof, and plated alloys.

(Sealing Members 104, 204, 304, and 404)

The sealing member is a member for sealing the light emitting element.

While the sealing member has an approximately hemispherical shapedcentered on the light emitting element according to the presentembodiment, the sealing member is not limited to this shape.

Known materials can be used as the sealing member and preferableexamples include translucent resins (for example, epoxy resin, urearesin, and silicone resin). In particular, since epoxy resin has highadhesion (adhesive strength) and is not easily detached, epoxy resin canenhance the effect of an embodiment.

For purposes of controlling light diffusion and thixotropy or the like,the sealing member may contain a filler such as aluminum oxide, siliconoxide, or titanium oxide.

In addition, the sealing member favorably contains a wavelengthconverting member such as phosphor which absorbs light from the lightemitting element and outputs light with a difference wavelength.Examples of such wavelength converting members include oxide-basedphosphors, sulfide-based phosphors, and nitride-based phosphors. When agallium nitride-based light emitting element that emits blue light isused as the light emitting element, a YAG-based or LAG-based phosphorthat absorbs blue light and emits yellow to green light, a SiAlON-basedphosphor that absorbs blue light and emits green light, or a SCASN-basedor CASN-based phosphor that absorbs blue light and emits red light isfavorably used independently or in combination with one other. Inparticular, a SiAlON-based phosphor and a SCASN-based phosphor arefavorably used in combination with each other for a light emittingdevice used in a display device such as a backlight of a liquid crystaldisplay or a television set. Furthermore, for illumination purposes, aYAG-based or LAG-based phosphor and a SCASN-based or CASN-based phosphorare favorably used in combination with each other.

Since residues of a sealing member containing such a wavelengthconverting member on the substrate after detachment may cause avariation in the shape of a sealing member when resetting the sealingmember or may cause a color variation of a completed light emittingdevice, the effect of an embodiment of enabling detachment to be readilyperformed is enhanced.

(Release Layer 105 and Air Layers 206, 306, and 406)

In the light emitting device according to embodiments, a release layeror an air layer is provided between the substrate and the sealingmember. Accordingly, the sealing member can be readily detached.

(Position of Release or Air Layer)

While the release layer or the air layer need only be provided in atleast a portion between the substrate and the sealing member, therelease layer or the air layer is favorably provided on an entire lowerface of the sealing member with the exception of a lower part of thelight emitting element. Accordingly, the sealing member can be readilydetached.

(Shape of Release or Air Layer)

While the release layer or the air layer may have any shape as long asthe sealing member can be readily detached, the release layer or the airlayer is favorably provided in a planar shape with approximately thesame size and approximately the same planar view shape as the lower face(the face opposing the substrate) of the sealing member. Otherwise, therelease layer or the air layer can be provided in various planar viewshapes such as a dotted shape, a linear shape, a grid-like shape, and aconcentric shape or a radial shape that is centered on the lightemitting element. While the sealing member does not come into directcontact with the substrate when the release layer or the air layer isprovided on an entire lower face of the sealing member, even in thiscase, the phrase “detaching the sealing member from the substrate” willbe used in the present specification.

When providing an air layer, in order to prevent contamination orcorrosion due to the light emitting element, the joint member, or thelike coming into contact with an outer atmosphere of the sealing memberand to produce a highly reliable light emitting device, members such asthe light emitting element, the joint member, the wiring, and the likeare favorably provided so as to be cut off from the outside of the lightemitting device by the sealing member.

For example, as shown in FIG. 3, the light emitting element 302, thejoint member 303, and the like can be covered by the sealing member 304and an air layer 306 may be provided outside of this portion.

In addition, such an air layer may be configured by having apart of thesealing member come into contact with the substrate so as to enclose thelight emitting element. For example, as shown in FIG. 4, the air layer406 can be provided so that a part of the sealing member 404 is incontact with the substrate 401 so as to enclose the light emittingelement 402, and the air layer 406 is provided from a contact portionbetween the part of sealing member 404 and the substrate 401 to an areanear the light emitting element 402 or, in other words, the air layer406 is enclosed by the sealing member 404 and is not continuous with theoutside of the light emitting device 410. While a shape of the portionof the sealing member in contact with the substrate is not particularlylimited, for example, the portion can have a concentric shape that iscentered on the light emitting element.

Furthermore, the sealing member is favorably provided so as to come intocontact with the substrate at an outermost peripheral portion and aroundthe light emitting element, and an air layer is favorably providedbetween the contact portions and the light emitting element. With thisarrangement, the sealing member can be fixed in a stable manner.

(Thickness)

While a thickness of the release layer or the air layer is notparticularly limited, the thickness is favorably around 15 to 50 μm(micrometers) to enable formation using a simple and inexpensive methodsuch as printing and is more favorably around 15 to 30 μm for thepurpose of reducing a decline in light extraction efficiency.

(Material of Release Layer)

As the release layer, materials with lower or higher adhesion with thesealing member as compared to the adhesion between the sealing memberand the substrate are used. When the adhesion with the sealing member islow, the sealing member is detached at an interface between the releaselayer and the sealing member, and when the adhesion with the sealingmember is high, the sealing member is detached at an interface betweenthe substrate and the release layer. Examples of specific materialsinclude oil repellent resins or the like that can be suitably selectedin consideration of the adhesion between the sealing member and thesubstrate. Specifically, fluororesins and silicone resins can be used.In particular, fluororesins that facilitate detachment are favorable.

Otherwise, the release layer favorably has translucency or opticalreflectance. Specifically, the release layer favorably contains whitetitanium oxide, silicon oxide, or the like. Accordingly, a higher lightextraction rate can be achieved. This is particularly favorable when thesubstrate has low optical reflectance.

(Method of Forming Release Layer)

The release layer can be formed on the substrate or on the lower face ofthe sealing member using methods such as printing, coating, spincoating, spraying, and ink jet.

(Air Layer)

Using an air layer is favorable in that a light emitting device enablinga sealing member to be readily detached can be created without providinga new member on the substrate and that resealing can be readilyperformed since the detached sealing member is less likely to remain onthe substrate.

(Method of Forming Air Layer)

The air layer can be formed by methods such as providing another memberon the substrate in advance in correspondence to a portion where the airlayer is to be provided and removing the member after disposing thesealing member. For example, the air layer can be formed by performingsealing in a state where silicone oil is applied and hardened andsubsequently dissolving the silicone oil using a solvent or the like toremove the silicone oil. Alternatively, the air layer can also be formedby a method in which a molded sealing member is bonded onto the lightemitting element.

(Combination of Release Layer and Air Layer)

Moreover, the light emitting device according to an embodiment may beconfigured to include both an air layer and a release layer. With thisarrangement, the sealing member can be more readily separated and, atthe same time, reliability of the light emitting device can beincreased. For example, the release layer can be provided below aportion of the sealing member covering the light emitting element or thejoint member, and the air layer can be provided below a portion of thesealing member that is outside of the release layer. Alternatively, forexample, the air layer can be provided on the substrate so as to enclosethe light emitting element, and a release layer in contact with thesealing member can be provided on the substrate around the air layer.

(Method of Detaching Sealing Member)

Methods of detaching the sealing member are not particularly limited andexamples of various means of detaching the sealing member includesuctioning and pulling up an upper face of the sealing member, applyinga horizontal load to a side face of the sealing member, and bending thesubstrate when the substrate is flexible.

When the light emitting element is defective, the sealing member and thelight emitting element are favorably detached at the same time.Accordingly, the number of steps can be reduced. Therefore, favorably,the sealing member and the light emitting element have high adhesionand, particularly favorably, when using a release layer, the adhesionbetween the sealing member and the light emitting element is higher thanthe adhesion between the sealing member and the release layer. Moreover,using a solder as the joint member of the light emitting element isfavorable since, by melting the solder, the sealing member and the lightemitting element can be readily detached at the same time.

(After Detaching Sealing Member)

After the sealing member is detached, when necessary, a sealing membercan be newly disposed (resealed) at a location where the originalsealing member had been disposed. In addition, when the light emittingelement is detached at the same time as sealing member, a light emittingelement can be mounted at or near a location where the detached lightemitting element had been mounted and a sealing member can be furtherprovided. Accordingly, the defective sealing member or light emittingelement can be readily replaced with a non-defective sealing member orlight emitting element, and since a light emitting device can beutilized instead of being discarded, waste and cost can be reduced.

According to the embodiment described above, the sealing member can bereadily detached.

EXAMPLES

Hereinafter, examples related to the method of detaching a sealingmember of a light emitting device according to an embodiment will bedescribed in detail with reference to the drawings.

First Example

A light emitting device 110 according to the present example includes: asubstrate 101 in which, on a brown polyimide film 101 a, a pair ofpieces of copper wirings 101 b and a white resist 101 c which isprovided so that a part of the wirings is exposed and which is made ofsilicone resin containing titanium oxide are sequentially provided; agallium nitride-based light emitting element 102 having a sapphiresubstrate which is flip-chip mounted on the wirings of the substrate; aSn—Cu based solder 103 which is a joint member that joins the substrate101 and the light emitting element 102 to each other; and a sealingmember 104 which seals the light emitting element 102 and which is madeof a translucent silicone resin containing a YAG phosphor, wherein a 25m-thick fluororesin layer 105 as a release layer is provided on anentire face between the substrate 101 and the sealing member 104.Adhesion between the fluororesin layer 105 and the sealing member 104 islower than adhesion between the sealing member 104 and the substrate101.

In order to detach the sealing member 104 of the light emitting device110, a near infrared laser is irradiated from a rear face (polyimidefilm side) of the substrate 101 to heat the solder 103 up toapproximately 290 degrees to melt the solder 103. Subsequently, in amelted state of the solder 103, an upper face of the sealing member 104is suctioned by a suction nozzle 107 to detach the light emittingelement 102 and the sealing member 104 from the substrate 101.

According to the present example, the sealing member 104 can be readilydetached.

Second Example

A light emitting device 210 according to the present example includes: asubstrate 201 in which a pair of pieces of silver wirings which goldplating is performed only on a joint part between the wirings and alight emitting element is provided on an alumina board; a flip-chipmounted light emitting element 202; an Au—Sn based solder 203 which hasa composition ratio of approximately 1:9 and which is a joint memberthat joins the light emitting element 202 onto the wirings of thesubstrate 201; an underfill 208 provided so as to fill a space betweenthe light emitting element 202 and the substrate 201; and a sealingmember 204 which seals the light emitting element 202 and which is madeof a translucent epoxy resin, wherein an air layer 206 is providedbetween the substrate 201 and the sealing member 204.

In order to detach the sealing member 204 of the light emitting device210, the light emitting device 210 is heated with a hot plate to meltthe solder 203. Subsequently, in a melted state of the solder 203, aside face of the sealing member 204 is pushed by a jig 207 in adirection that is horizontal with respect to the substrate 201 to detachthe light emitting element 202 and the sealing member 204 from thesubstrate 201.

According to the present example, the sealing member 204 can be readilydetached from the substrate 201 in a similar manner to the firstexample.

-   110, 210, 310, 410 light emitting device-   101, 201, 301, 401 substrate-   102, 202, 302, 402 light emitting element-   103, 203, 303, 403 joint member-   104, 204, 304, 404 sealing member-   105 release layer-   206, 306, 406 air layer-   107 suction nozzle-   207 jig-   208, 308 underfill

The invention claimed is:
 1. A method of detaching a sealing member of alight emitting device comprising a substrate, a light emitting elementmounted on the substrate and a sealing member that seals the lightemitting element, the method comprising: providing an air layer betweenthe substrate and the sealing member; and detaching the sealing memberfrom the substrate at the air layer.
 2. The method of detaching asealing member of a light emitting device according to claim 1, whereinproviding the air layer from a contact portion between the part ofsealing member and the substrate to an area near the light emittingelement.
 3. The method of detaching a sealing member of a light emittingdevice according to claim 1, wherein detaching the sealing member andthe light emitting element at the same time.
 4. The method of detachinga sealing member of a light emitting device according to claim 1,wherein depositing a new sealing member after detaching the sealingmember.
 5. The method of detaching a sealing member of a light emittingdevice according to claim 1, wherein the thickness of the air layer isaround 15 to 50 micrometer.
 6. The method of detaching a sealing memberof a light emitting device according to claim 1, wherein the sealingmember contains a wavelength converting member.
 7. The method ofdetaching a sealing member of a light emitting device according to claim1, wherein the sealing member has hemispherical shape.
 8. The method ofdetaching a sealing member of a light emitting device according to claim1, further comprising melting a joint member that joins the lightemitting element and the substrate, and detaching the light emittingelement from the substrate.
 9. The method of detaching a sealing memberof a light emitting device according to claim 8, wherein the lightemitting element is detached from the substrate at the same time thatthe sealing member is detached from the substrate.
 10. The method ofdetaching a sealing member of a light emitting device according to claim8, wherein the joint member is a solder.